Process for the catalytic oxidation of organic compounds



June 22 1926,

c. R'. DowNs PROCESS FOR THE CATALYTIC OXIDATION OF ORGANIC COMPOUNDSFiled Jan. 21. 1924 45 MLXTURE oF oxmfznvc ans ANU (/vnpore oF' oRGAnncSUBSTHNCE CONDENSER FOR/ SULFUR VAPOFS Bom, ru ULI-U l G- S R5:

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FV PAR-nauw oxnmzso PRoouc-ns ATTORNEY.

Patented June 22, 1926.

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Application ma January sar-1924. semi no. 7.441.

This invention relates to an improvement in the process of producingpartlal oxidation products of organic compounds by the catalyticoxidation of these compounds. 1n the vapor lphase with an oxygencontaining gas. In such reactions it is necessary to maintain thetemperature of the' catalyst and reacting gases within a narrow range oftem erature in order to produce the bestA resu ts and as the oxidationreactionl is highly exothermic, .the heat' evolved must lbe removed asformed in order to maintain the desired uniform temperature. Iaccomplish this by providing sulphur which can boil in heat transferringrelationship to thecatalyst and reacting gases, and by regulating` thepressure on the sulphur system, I maintain automatically the temperatureconditions more nearly constant as is desired.

In the past I have suggested and used boiling mercury for a similarpurpose with satisfactory results. Mercury, however, has certaindisadvantages when used in this way, namely, that its vapors, althoughodorless, are very poisonous to the human system, short ex osuresresulting in serious poisonling lor eath; further, on a volume basis,due to its high density and price, it is very costly and consequently,slight leaks in the apparatus in which the process is carried out resultin industrial hazards and large financial losses.

I have found that sulphur is superior to mercury in these respects inthat it is cheap, costing on a volume basis 1/500 as much as mercury,and, further, leaks are readily detected. As in the case of mercury, theboiling point of sulphur can be varied over relatively wide limits bythe application of the proper absolute pressure to the system in whichthe sulphur is contained. Under atmospheric pressure, it boils at 444.6C., or about 87 above the boiling point of mercury under like pressure.Since many catalytic oxidation reactions proceed most favorably at 400C. or above, the pressure on the system necessary when using sulphur ismaterially less than `when mercury4 is employed. This means that withsulphur at a given temperature in the general range mentioned, theconstruction of the apparatus in whichthe process is carried out can belighter because the absolute pressures are less and the danger ofleakage can therefore be reduced.

It willthus be seen that sulphur 'poe-` sessescertain importantadvantages for use in these processes.

The invention will be described and il lustrated in connection withapparatus in which aireaction mixture in gaseous form is broughtintocontact with a catalyst, in

heat transferring relationship -with which.'

is maintained boiling sulphur, combined with means for condensing the`va orized sulphur and returning the condense liquid yand means'forcontrolling the pressureon the sulphur system. It is to be understoodthat theparti'cular apparatusshown is only to illustrate the process andthe vinvention is not restricted to the particular apparatus shown, no rto any specific material or materialsof construction mentioned. l

The drawing represents a vertical section through a form of apparatussuitable for carrying out the process. Numeral 1 re resents a shell tocontain the sulphur w ose upper level is shown at 2. The tubes -3-are vsealed into the tube sheets 4 byjoints which are ti'ght againstvdilerentlal pressures. The tube sl1eets'4 are also sealed tightly to theshell 1 around the circumference at Athe points 5. A screen orperforated plate 6 is supported by means not shown so that it is inContact with the bottom of the tubes 3. The tubes are partiallyfilled-with a porous non-catalytic material 7 resting on the screen 6and above this the catalyst 8 whose upper level is slightly below thesulphur level 2 is located. The tubes above the catalyst may be eitherempty or filled with a porous non-catalytic mass. A cooling andcondensing means 9 with inlet 10 and outlet 11 is providedl at the topof the A:chamber by means of which the vaporized sulphur may' becondensed and returned to the body of liquid sulphur. A top section 12with vapor inlet 13 and a bottom section 14 with va or outlet 15 areattached to the tube. she 1.

A pipe 16 leads from the sulphur system 1 `above the liquid level to apressure tank 17 with manometer 18 and means, not shown, for maintaininga constant pressure of a neutral gas on the sulphur system. All

tact with the sulphur should be constructed of aluminum or other homoeneous metal or alloy or a coated metal which is resistant to the actionof boln'g sulphur or sulphur vapor,

Vparts of the apparatus which come into conl -A horizontal section ofthe converter and tubesis not shown but this may be rectan 'y lar orcircular or it mayhave any ot er suitable form. The condensing means 9"may be a spiral pipe coil as shown or any1 other suitable form knowntothe art. lThe tubes 3 maybe welded into the tube sheets 4 or may besealed to them by other means.

` their cross-section. The tube sheets 4 may sisting in scribe the Thetubes containing the catalyst may circular, rectangular or any otherform 1n be bolted, riveted or welded to the shell 1.y Other forms ofcondensers for the sulphur vapor may be used wherein the vapors are ledoutside the shell 1, there condensed,

toluene. T

i. molybdenum. The apparutus issclosed and the sulphur heated tolboiling by means not shown and the pressure on the sulphur systemregulated to the desired point, Vsay to maintaln a catalyst temperatureof 525 C. A mixture of toluene vapors and air is then passed into theinlet 13, is preheated' tubes 3 b the reof the sulphur' vapor., heprelieate vapors then.` meet the catalyst 8, reaction takes place andheat is-generated. This heat is transferred by radiation, convection andconduction to the sulphur, causing it to boil and thereby removing theheat as latent heat of vaporization without change of" temperature. Theproducts of 1n the upper part of the fluxing reaction pass out at 15 tosuitable condensing and recovery means. After the reaction isestablished 'the supply of outside heat 'may be discontinued as theoperation is thermally self-sustaining. Any sulphur vapor not condensedin preheating the entering gases is condensed by the condenser 9 and isreturned to the liquid sulphur for 'tion such` as the production ofphthalic anhydride from naphthalene, anthraqui- 'catalyst and reactinggases .z tion none from' anthracene andl maleic anhydride i frombenzene.

Having thus described and particularized lphasewith an oxygen containingas in the presence of a catalyst,l the step w ich comprises regulatingthe temperature of the catalyst and reacting gases by removing the heatof reaction by the vaporization of sulphur, distributed within the zoneof reaction out of direct contact with the catalyst but in heatconducting relationship thereto.

2. In the production of benzaldehydeby the oxidation of toluene in withan 'oxygen containing g'as in .the pres. ence of a catalyst,the stepwhich comprises regulatin the tem erature of thecatalyst and reactinggases y removing the, heat of reaction by the vaporization of sulphur,distributed within the zone of reaction out of direct contact with thecatalyst butin heat 4conducting relationship thereto.

3. In the production of partial oxidation products of organic compoundsin the vapor phase with an oxygen containing as in the presence of acatalyst, the step w ich comprises regulating the tem rature of the yremovin the orization o sule zone of lreacheat of reaction by the vaphur 1,distributed within t out of direct contact with the catalyst, butin heat transferring relationship thereto, the temperature at which thesulphur boils being controlled bythe pressure applied to it. v

4. In the production of benzaldehyde by the oxidation of toluene inthevapor phase with an oxygen Acontaining gas in the presence of acatalyst, the step which .comprises regulatintheftem erature of thecatalyst and reacting-gases y-removing the heat of reaction by thevaporization vof sulphur distributed within the zone of reaction out ofdirect contact with the catalyst, but in heat transferring relationship'thereto, the temperature at which the sulphur boils being controlled bythe ressure a plied to it.

In testimony w ereof, I ereby aliix my signature. l

CHARLES RAYMOND DOWNS. f

the vapor phase

